/**
 * 这是一个圆的类
 */
public class Circle {
    private static double radius = 0;
    private static double area = 0;
    private static double perimeter = 0;

    public static void setRadius(double r) {
        radius = r;
        area = r * r * Math.PI;
        perimeter = 2 * Math.PI * r;
    }

    public static double getRadius() {
        return radius;
    }

    public static double getPerimeter() {
        return perimeter;
    }

    public static double getArea() {
        return area;
    }


}
